Sectional floating roof and method of forming same

ABSTRACT

A floating roof for use in a storage tank having an upstanding substantially cylindrical seal comprises a plurality of individually buoyant inner and outer roof sections, each including a continuous peripheral wall therearound and a bottom wall closing the area defined by the peripheral wall, the roof sections being arranged substantially to fill the area defined by the associated shell with the peripheral walls of adjacent roof sections abutting against one another, the abutting peripheral wall portions of adjacent roof sections being secured together by interlocking pairs of lugs on each section; the lugs are formed by on-site die punching of the abutting peripheral wall portions resulting in the pair of lugs of one section over-lapping the corresponding pair of lugs on the abutting section, the lugs of each pair then being bent toward each other for interlocking the overlapping pairs.

United States Patent 1 Heisterberg SECTIONAL FLOATING ROOF AND METHOD OF FORMING SAME [75] Inventor: Milton W. Heisterlrerg, Flossmoor,

[73] Assignee: General American Transportation Corporation, Chicago, Ill.

22 Filed: Nov. 3, 1971 21 Appl. No.: 195,105

[52] US. Cl. 220/26 R, 29/513, 113/116 FF [51] Int. Cl B65d 87/18 [58] Field of Search 220/26 R, 26 S, 26 D,

220/26 SA; 113/116 FF; 29/513 [56] References Cited UNITED STATES PATENTS 1,639,625 8/1927 Afonin 220/26 R 2,914,212 11/1959 Fino 220/26 S 3,010,199 11/1961 Smith et 113/116 FF X 3,079,029 2/ 1963 Moyer et al. 220/26 S 3,439,829 4/1969 Thompson et 220/26 S 3,493,143 2/ 1970 Thompson et a1 220/26 S 5.] Nov. 27, 1973 Primary Examiner-Samuel B. Rothberg Assistant Examiner.lames R. Garrett Att0mey-David A. Vogel [5 7] ABSTRACT A floating roof for use in a storage tank having an upstanding substantially cylindrical seal comprises a plurality of individually buoyant inner and outer roof sections, each including a continuous peripheral wall therearound and a bottom wall closing the area defined by the peripheral wall, the roof sections being arranged substantially to fill the area defined by the associated shell with the peripheral walls of adjacent roof sections abutting against one another, the abutting peripheral wall portions of adjacent roof sections being secured together by interlocking pairs of lugs on each section; the lugs are formed by on-site die punching of the abutting peripheral wall portions resulting in the pair of lugs of one section over-lapping the corresponding pair of lugs on the abutting section, the lugs of each pair then being bent toward each other for interlocking the overlapping pairs.

4 Claims, 10 Drawing Figures Patented Nov. 27, 1973 3,774, 99

3 Sheets-Sheet 1 FIGJ I30 IN VENTOR ATTYS.

MILTON w. HE/STERBERG' Patentd Nov. 27, 1913 3 Shae ts-Sheet 2 Patented Newe 2.7, W?

3 Sheets-Sheet 3 SECTIONAL FLOATING ROOF AND METHOD OF FORMING SAME This invention is directed to a sectional floating roof for use in a storage tank, and to individual buoyant roof sections useful in forming such a floating roof. More particularly, the present invention is directed to a means and method for securely interlocking the roof sections to form the floating roof.

It is a general object of this invention to provide a novel means and method for effecting the interconnection between adjacent roof sections.

It is an important object of this invention to provide a floating roof for use in a storage tank having an upstanding substantially cylindrical shell, the floating roof comprising a plurality of individually, buoyant roof sections, each of the roof sections including a continuous peripheral wall therearound and a bottom wall closing the area defined by the peripheral wall, the roof sections being arranged substantially to fill the area defined by the associated shell with the peripheral wall of each roof section being disposed against the peripheral walls of the adjacent roof sections, each of the roof sections having a plurality of openings formedv in and spaced around the peripheral wall thereof and a plurality of lugs spaced around and integral with the peripheral wall and extending therefrom, the roof sections being so arranged in the assembled positions thereof that lugs of at least certain ones of the roof sections are respectively received in 'corresponding ones of the openings in adjacent roof sections and bent into locking engagement therewith for securing the roof sections one to another, and sealing means disposed between the roof sections and the associated shell to provide a vapor seal between the floating roof and associated shell.

Another object of this invention is to provide a floating roof of the type set forth, wherein each of the roof sections has a plurality of pairs of openings formed therein and a plurality of pairs of lugs extending therefrom, the lugs of each pair of lugs being respectively integral with the peripheral wall adjacent to and between the openings of a corresponding one of the pairs of openings, certain of the pairs of lugs extending outwardly of the peripheral wall and others of the pairs of lugs extending inwardly of the peripheral wall, the roof sections being so arranged in-the assembled positions thereof that the outwardly extending pairs of lugs are respectively received in corresponding ones of the pairs of openings in adjacent roof sections in overlapping relationship with corresponding pairs of inwardly extending lugs on the adjacent roof sections.

In connection with the foregoing object, it is another object of the invention to provide a floating roof of the type set forth, which comprises a plurality of inner roof sections surrounded by a plurality of outer roof sections.

Still another object of the invention is to provide a method of forming from a plurality of individually buoyant roof sections a floating roof for use in a storage tank having an upstanding substantially cylindrical shell wherein each of the roof sections includes a continuous peripheral wall therearound and a bottom wall closing the area defined by the peripheral wall, the method comprising the steps of arranging the roof sections substantially to fill the area defined by the associated shell with the peripheral wall of each roof section abutting against the peripheral walls of the adjacent roof sections, die punching the abutting portions of the peripheral walls of adjacent roof sections at spaced-apart sites therealong to form at each site pairs of lugs respectively integral with the peripheral walls and extending therefrom, the pairs of lugs at each punched-site being disposed in overlapping relationship with each other and extending inwardly of one of the abutting peripheral walls, bending the overlapping pairs of lugs at each site into locking engagement with each other for securing the roof sections one to another, and sealing the area between the roof sections and the associated shell.

In connection with the foregoing object, another object of the invention is to provide a method of the type set forth, wherein the floating roof is formed of a plurality of inner roof sections and a plurality of outer roof sections arranged between the inner roof sections and the associated shell.

Further features of the invention pertain to the particular arrangement of the parts of the floating roof and of the steps of the method of forming the floating roof whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which:

FIG. 1 is a side elevational view in partial section of a storage tank provided with a floating sectional roof constructed in accordance with and embodying the features of the present invention;

FIG. 2 is an enlarged fragmentary view in horizontal section taken along the line 2-2 in FIG. 1, and illustrating a peripheral portion of the floating roof including several inner and outer roof sections;

FIG. 3 is a further enlarged view in vertical section taken along the line 31-3 in FIG. 2, and illustrating the flotation of the roof sections on the body of liquid stored in the tank;

FIG. 4 is a perspective view of one of the inner roof sections of the present invention, and illustrating the connection thereof to adjacent inner and outer roof sections in accordance with the present invention;

FIG. 5 is a further enlarged fragmentary perspective view of a portion of the abutting peripheral walls of two adjacent inner roof sections, showing the interconnection thereof by punched-out lugs according to the present invention;

FIG. 6 is a fragmentary view in horizontal section of the abutting peripheral walls of adjacent roof sections, and illustrating the die-punching apparatus for performing the method of the present invention with the die-punch apparatus shown disposed in position immediately prior to the punching operation;

FIG. 7 is an end elevational view of the die punch taken along the line 7-7 in FIG. 6;

FIG. 8 is a view similar to FIG. 6, and illustrating the die-punch apparatus in its configuration immediately after completion of the punching operation; I

FIG. 9 is a view similar to FIG. 8, and illustrating the completed punched-out lugs afterremoval of the diepunching apparatus; and

FIG. 10 is a view similar to FIG. 9 and illustrating the completed joint between the. adjacent roof sections after bending of the lugs into locking engagement with one another.

Referring to FIG. 1 of the drawings, there is illustrated a storage tank of the floating roof type having a column-supported fixed cone roof thereon and having disposed therein an internal floating roof 100 made in accordance with and embodying the principles of the present invention. The storage tank 20 is particularly adapted for storing liquids such as petroleum products that have a significant vapor pressure, the floating roof 100 being provided to trap and hold the vapors from the petroleum products to prevent escape thereof from the tank 20. The floating roof 100 is an improvement of the floating roof disclosed in U. S. Pat. No. 3,493,143 entitled Sectional Floating Roof and Roof Sections Therefor, issued to Joseph C. Thompson and Milton W. Heisterberg and assigned to the assignee of the present invention, the disclosure of which patent is incorporated herein by reference.

Considering now the mechanical construction of the tank 20, there is provided an upstanding substantially cylindrical side wall or shell 21 having a generally cylindrical inner surface 22, the shell 21 being mounted upon a suitable base or floor 23 andcarrying on the upper portion thereof a cone roof 24 which serves to cover the entire area bounded by the shell 21 and is fixedly secured thereto. As illustrated, the tank 20 has a diameter such that the cone roof 24 must be supported by a plurality of columns or posts 25 extending from the floor 23 upwardly to the underside of a fixed roof 24 for support thereof. There further is provided suitable inlet fixtures (not shown) and the usual outlet fixture 26 for adding lading to the tank 20 and for withdrawing lading therefrom. Finally, there is provided a manhole 27 having a conventional cover 28 associated therewith, whereby access may be had to the interior of the tank 20 for construction and repair thereof, the manhole typically having an internal diameter of about 20 inches.

As illustrated in FIG. 1, there is a body 30 of petroleum stored within the tank 20 and floating upon the upper surface 31 of the petroleum 30 is the floating roof 100 for the purpose of maintaining any petroleum vapors adjacent to the liquid petroleum 30, thereby to prevent further volatilization of the liquid petroleum 30 and to prevent escape of the vaporized petroleum from beneath the floating roof 100 and out of the storage tank 20. To this end, the floating roof 100 extends over the entire surface of the petroleum 30 and moves vertically within the storage tank 20 as the level of the petroleum 30 within the tank 20 changes. In order to prevent the vapor loss referred to above, a first sealing arrangement 165 is provided between the floating roof 100 and the inner surface 22 of the shell 21, and a second sealing arrangement 170 is provided between the floating roof 100 and each of the supporting posts 25.

Considering now in detail the construction of the floating roof 100, particular reference being made to FIGS. 2 through 10 of the drawings, it will be seen from FIG. 2 that the floating roof 100 is made up of a plurality of roof sections, three distinct types of roof sections being provided including an inner standard roof section 110, an inner shortened roof section 120 and an outer roof section 130. It is an important feature of the present invention that each of the three types of roof sections named have the same basic cross section in a direction transverse to the longitudinal axes thereof, the differences among the roof sections residing in the lengths thereof and the disposition of the end walls thereof.

Referring to FIGS. 3 and 4, there are illustrated the details of construction of the inner standard roof section 110. It will be noted that the roof section 110 is generally rectangular in plan view and is also rectangular in the side and end views. In general, the roof section comprises a peripheral wall, formed from a pair of generally upstanding parallel spaced-apart side walls 111 and a pair of generally upstanding parallel spaced-apart end walls 112 that extend between the side walls 111 and are suitably joined thereto as by welding-to provide a continuous rectangular peripheral wall about the roof section 110. The area defined by and surrounded by the aforementioned peripheral wall is closed by a bottom wall 115 of composite structure. More specifically, the bottom wall 115 includes a pair of rectangular longitudinally extending center portions 116 which extend between the end walls 112 and are secured thereto as by welding at the outer ends thereof. The inner edges of the center portions 116 are joined as at 114 and the outer edges have formed integral therewith and respectively depending therefrom side flanges 118, the outer longitudinal edges of the center portions 116 being joined to the upper edges of the respective side flanges 118 along longitudinally extending junctions 117. The lower edges of the side flanges 118 are joined to. the lower endges of the side walls 111 by curved junctions 119, respectively, and the outer ends of the side flanges 118 are secured to the end walls I 12 as by welding. v

Referring to FIG. 3, it will be seen that the side walls 1 1 1 and the bottom walls 1 15, including the center portions 116 and the side flanges 118 are all preferably formed of a single rectangular sheet of material, such as sheet metal, bent to provide the parts named in the relationship illustrated. More specifically the junctions 1 17 are disposed well above the lower edges of the side walls 111 and only a short distance below the upper edges of the side walls 111, while the central junction 114 is disposed slightly below the junctions 117. The end walls 112 in this form of the invention are formed as rectangular plates of the same material as the other parts, for example, sheet metal, and are secured to the ends of the side walls 111 and the bottom wall 115 by welding, care being taken to provide a fluid-tight joint therebetween. When so constructed, it will be appreciated that a significant volume is provided below the bottom wall 115 and between the end walls 112, which volume is useful in the flotation of the roof section upon the petroleum 30. More specifically, each of the roof sections 110 is individually buoyant, and preferably is designed so that the upper surface 31 of the petroleum upon which the roof section 110 floats will be arranged as illustrated in FIG. 3. It will be appreciated that a significant volume 113 is provided between the surface 31 and the bottom wall for trapping of petroleum vapors therein, while the side walls 11 1 and the end walls 112 extend essentially normal to the surface 31 and with the upper edges of the walls disposed a good distance thereabove.

The dimensions of the standard roof section 110 are chosen so that the sections may be readily handled by workmen during the construction or repair of the floating roof 100, and more specifically, the dimensions are such that the standard roof sections 110 can be passed through the manhole 27, thus allowing construction and repair of the floating roof 100 after the tank has been fully erected. In a typical construction of the standard roof section 110, the length thereof, i.e., the length of the side walls 111, is 16 feet, the width of the roof section 110, i.e., the length of the end walls 112 is 18 inches, while the vertical extent of the walls 111 and 1 12 is 4 inches. A standard roof section 110 having such dimensions can be readily passed through the manhole 27 and lowered into the storage tank 20. It will be understood that the individual roof sections may be temporarily supported on a frame during assembly of the roof 100 in order to provide the proper level of each of the roof sections, or 4 to 6 inches of water may be introduced into the tank so that the individual buoyant roof sections can be floated thereon and thereafter assembled to provide the completed roof 100.

In accordance with the present invention, as many as possible of the standard roof sections 110 are utilized in forming the roof 100 since the standard roof sections 110 can be in effect mass-produced, thus accomplishing significant economies in the manufacture of the several types of roof sections, the same cross section illustrated in FIG. 3 being provided in each, i.e., the same cross section including the side walls 1 11, the bottom wall center portions 1 16 and the side flanges 118.

Each of the inner shortened roof sections 120 is essentially like the standard roof section 110 except that the length thereof is less. Referring to FIG. 3, it is to be noted that several parts of the inner shortened roof section 120 have had applied thereto numerals in the 120 series that correspond to the numerals in the 110 series of like parts for the standard roof section 110. The roof sections 120 are utilized to fill rectangular areas which are shorter than the standard roof section 110.

There is however a special problem encountered on the periphery of the roof 110 inasmuch as the roof 100 is essentially circular so as to conform to the circular shape of the tank shell 21. So as to approximate a circular outer periphery of the tank 100, a plurality of outer roof sections 130 are provided, the outer roof sections 130 having the same lateral cross section as the roof sections 110 and 120 and varying therefrom only in that one of the end walls disposed at an acute angle with respect to the normal end wall, e.g., 112. In order more nearly to approximate the desired circular outline of the roof 100, the lengths of the outer roof sections 130 are varied as is the acute angle for the angularly disposed end wall. However, it has been found that only a very few different forms of the outer roof sections 130 are required, namely about a half dozen, in order to provide a good approximation of a circular outline for the roof 100 (see F IG. 2), whereby again substantial economies in manufacture are obtained. The construction of the roof sections 130 is more fully described in the aforementioned U. S. Pat. No. 3,493,143.

A typical pattern for assembling a plurality of the standard roof sections 110 with the required shortened roof sections 120 and outer roof sections 130 to provide a generally circular assembly is illustrated in FIG. 2. It will be noted that as many as possible of the standard roof sections 110 and the shortened roof sections 120 are used, this resulting in a marked economy in manufacture and construction since these sections are more economically produced and assembled. However, to provide a substantially circular outline for the roof 100, a plurality of and a number of different varieties of the outer roof'sections 130 are provided.

As is best seen in FIGS. 2 through 4, the several roof sections are all secured by interlocking lugs or clips 150 at predetermined intervals along the adjacent side walls and end walls so as completely to fill the area of the roof so that there are no voids or spaces therein. The individually buoyant roof sections when assembled as illustrated form a vapor-tight liquid seal around the edges, whereby no gaskets or seals are provided be tween the adjacent roof sections. The plurality of side walls and end walls joined one to another also provides stiffness for the floating roof 100. It will be understood that as shipped from the factory, the several roof sections have imperforate side and end walls, the necessary coupling lugs 150 preferably being punched in the field as a part of the assembly operation as will be described in detail hereinafter. The assembled roof 100 is substantially lighter in weight than the floating roofs commonly used heretofore.

A significant feature of the present invention resides in the method of assembling the roof sections 110, 120, and to form the floating roof 100. Referring to FIGS. 5 through 10 of the drawings, there are illustrated two abutting side walls 111A and 111B of two adjacent roof sections 110A and 1108, respectively, the side walls 111A and 1118 being arranged back to back in contact with each other. For securing the side walls 111A and 111B together, there is provided a die punch mechanism, preferably hydraulically operated, and generally designated by the numeral 140, the die punch mechanism including a die 141 and a punch 145. (See FIGS. 6-8) The die 141 is provided with a bearing surface 141a, and an elongated generally oval clearance opening 142 therein, having arcuate ends as at 143. Centrally disposed in the opening 142 is a center post 144 having a distal end 144a disposed substantially co-planar with the bearing surface 141a of the die 141. In use, the die 141 is disposed with the bearing surface 141a and the distal end 144a of the center post 144 disposed in engagement with the surface of one of the side walls to be joined, the die 141 being shown in the drawings as disposed in engagement with the surface of the side wall 111B, by way of illustration. It will, of course, be understood that the die 141 may also be disposed against the other side wall 111A, if desired.

The punch 145 is generally U-shaped and is provided with a pair of spaced-apart legs 146, the facing surfaces 146a of the legs 146 being joined at the inner ends thereof by an arcuate end surface 147. Formed at the distal ends of the legs 1.46 are cutting edges 148, each of the cutting edges 148 having an arcuate outer. portion 149 and straight side portions 149a, the innerends of the side portions 149a being displaced in the direction of the arcuate end surface 147 so that the cutting edge 148 is inclined upwardly from the arcuate end portion 149 thereof to inner ends of the straight side portions 149a thereof. It will be understood that this sloping arrangement of the cutting edges 148 imparts a bending movement to the punched out material, as is I well known in the art. The legs 146 of the punch 145 I are spaced apart a distance greater than the thickness of the center post 144, the outer arcuate portions 149 of the'cutting edges 148 being shaped complementary to the arcuate ends 143 of the recess 142 in the platen 141 and dimensioned and arranged to be received therein in straddling relationship with the center post 144. In use, the punch 145 is disposed on the side of the two side walls to be joined opposite the die 141, i.e., in

facing relationship with the exposed surface of the side wall 111A, as illustrated in FlG. 6 of the drawings.

When the die 141 and the punch 145 have been positioned as illustrated in FIG. 6, the punch 145 is driven by associated drive means (not shown) of the die punch mechanism 140 in the direction of the arrow in FIG. 6 for simultaneously punching the adjacent portions of the abutting roof section side walls 111A and l 1 1B. As the cutting edges 148 of the punch 145A are driven against and through the side walls 111A and 1113, the outer surface of the side wall 111A is first engaged by the arcuate outer portions 149 of the cutting edges 148 so that the side wall 1 1 1A is first cut adjacent to the extremities of the die clearance opening 142. Thus, as the punch 145 passes through the abutting side walls 111A and 1118, it cuts from the side wall 111A a pair of lugs 150A and cuts from the side wall 111B a like pair of lugs 1508. Because of the inclined arrangement of the cutting edges 148, the tips or outer ends 155A and 1553 of the lugs 150A and 150B are depressed into the associated clearance opening 142 ahead of the remaining portions of the lugs 150A and 1508, therebyimparting a bending movement of the lugs. Accordingly, as the legs 146 of the punch 145 pass completely through the abutting side walls 111A and 111B and into the adjacent portions of the opening 142, the cutout distal ends 155A and 1553 of the lugs 150A and 1508 are driven downwardly into the opening 142 and about the opposite sides of the center post 144, to the position indicated in FIG. 8. As the punch 145 passes into the opening 142, the center post 144 and the cutout lugs 150A and 1508 are accommodated in the space between the punch die legs 146, the portions of the side walls 111A and 1118 immediately overlying the distal end 144a of the post 144 respectively integral with and connecting the lugs 150A and 150B and remain intact and integral with the side walls 111A and 1118. The displacement of the cut-out lugs 150A and 1508 from the side walls 1 11A and 1118 forms therein pairs of slots or openings 153A and 153B, the pair of openings 153A being separated by the bridge 151A and the pair of openings 1538 being separated by the bridge 1518. It will be observed that, after the punching operation, the lugs 150A extend through the openings 153B and beyond the exposed surface of the side wall 1 1 1 B. a

It will be noted that, in this configuration, the lugs 150A are disposed in straddling relationship and engagement with the outer surfaces of the lugs 150B, with the lug tips 155B extending beyond the lug tips 155A by reason of the finite thickness of the lugs 150A and 1508. Further, it will be observed that the lugs 150A and 1503 extend in the same direction, i.e., toward the exposed surface of the side Wall 1118, which may be disposed inwardly or outwardly of the associated roof section, as desired. Subsequent to the punching operation, the punch die 145 is withdrawn from the recess 142 and from the openings 153A and 1533, and the platen 141 is removed from contact with the side wall 1118 for movement to the next punching site or station.

The distal ends 155A and 1558 of the lugs 150A and 1503, respectively, are then peened over or otherwise bent by suitable means in the directions of the arrows in FIG. 9 to the configuration illustrated in FIG. 10. In this latter configuration, the lug tips 1553 are disposed closely adjacent to each other, the spacing between the lug tips 1553 being substantially less than the spacing between the lugs 150B at the connected ends thereof adjacent to the bridge 151B. Further, the lug tips 155A are deflected inwardly toward each other and respectively into firm engagement with the outer surfaces of the lugs 150B so that the spacing between the lug tips 155A is less than the spacing between the outer surfaces of the lugs 1508 at the connected ends thereof adjacent to the base 1518. Thus, it will be appreciated that the lugs 150A are locked or clipped firmly in engagement with the lugs 1508 so as to prevent withdrawal of the lugs 150A from the openings 1538, thereby to securely hold the abutting side walls 111A and 111B in firm engagement with each other.

Preferably, the abutting side walls 111A and 1118 are punched in a manner just described at a plurality of spaced-apart sites therealong, these sites all being disposed adjacent to the upper edges of the side walls 1 1 1. In like manner, the side walls 111 and end walls 112 of each of the other roof sections and the side walls 121 and end walls 122 of each of the roof sections are securely punch-clipped to the abutting walls of adjacent roof sections 110, 120 or until all of the roof sections comprising the roof 100 are securely interconnected. In the preferred embodiment of the invention, the abutting peripheral walls of the adjacent roof sections are punch-clipped together at points spaced apart by six to 12 inches, but it will be appreciated that any desired spacing of the punching sites may be utilized. In view of the fact that the upper edges of the walls 111 and 112 are disposed well above the surface 31, assemblies of the roof sections 110 can be readily made and the individual roof sections, secured one to the other by means of the coupling lugs passing through the upper portions of the walls 111 and 112. Inasmuch as the lugs 150 and the holes 153 associated therewith are disposed well above the surface 31 of the petroleum 30, no special sealing structure must be provided therefor. Further, since the outer surfaces of the side walls 111 and the end walls are substantially flat and planar, the flat surfaces will tightly bear against the abutting surfaces of adjacent roof sections and will be held in close contact by the lugs 150 whereby to eliminate the necessity of any gaskets or sealing structure therebetween, or in fact between the roof sections 1 10 generally.

The outer periphery of the thus assembled roof sections is spaced a slight distance away from the inner surface 22 of the shell 21, whereby it is necessary and desirable to provide the outer or shell seal structure that extends around the outer periphery of the roof 100 and seals the area disposed between the outer periphery of the roof 100 and the inner surface 22 of the shell 21.- Referring to FIG. 2, there is illustrated a first preferred form of such a sealing structure which includes a generally annularly shaped and horizontally disposed mounting plate 161 extending completely around the periphery of the roof 100 and fixedly secured thereto. Preferably, the mounting plate 161 is provided in the form of several individual arcuate sections which are suitably secured to the outer roof sections 130 and specifically to mounting flanges thereon (not shown), as by rivets. The outer periphery of the mounting plate 161 carries an upstanding annular wall 162 secured to the mounting plate 161 as by welding. Mounted on the wall 162 is a sealing element 165 which is in the form of a substantially annular resilient member arranged in the annular space between the shell 21 and the wall 162 and located above the upper level 31 of the stored petroleum 30. The sealing element 165 is more specifically formed of a body of flexible and resilient material, the preferred material being an expanded synthetic organic plastic resin, such for example as a co-polymer of butadiene and acylonitrile resins, suitable resins being that sold under the trademark Buna N or that sold under the trademark Rubatex, or the equivalent.

Fastener structure (not shown) is provided to mount the sealing element 165 upon the wall 162 of the floating roof 100 so as to hold the peripheral bearing surface of the sealing element 165 disposed in sliding and sealing engagement with the tank shell, thus to seal the annular space between the tank shell and the roof 100 above the surface of the stored petroleum 30. The detailed construction and mounting of this fastener structure and of the sealing element 165 is disclosed in the aforementioned US. Pat. No. 3,493,143.

It will be appreciated that other forms of sealing elements 165 and other forms of sealing structures 160 may be used in place of those illustrated, it only being required that the structure and sealing element provide the necessary tight seal between the floating roof 100 and the tank shell 21.

There are further provided between the floating roof 100 and the several supporting posts 25 the post seal structures 170, the details of which are described in the aforementioned US. Pat. No. 3,493,143.

With the other seal structure 160 and the several post seal structures 170 in position, the floating roof 100 is not only fluid-tight, butis also vapor-tight, whereby to trap and hold the petroleum vapors that are always present above the stored petroleum 30. In this manner, the escape of the petroleum vapor from the storage tank is positively prevented, thus to prevent loss of the petroleum from the tank 20. Furthermore, the several sealing elements maintain the sealing contact with the surfaces of the shell 21 and the posts 25, respectively, as the floating roof 100 rises and falls in accordance with the addition and withdrawal of the petroleum 30 to and from the storage tank 20.

From the foregoing, it will be seen that there has been provided a novel sectional floating roof construction, and in particular, a novel means for interconnecting adjacent roof sections by means of integral lugs formed on each roof section.

Furthermore, there has been provided a novel sectional floating roof wherein the roof sections are interconnected by pairs of interlocking lugs, the lugs of one adjacent section being disposed through complementary openings in the other adjacent section and in overlapping relationship with a corresponding pair of lugs on the other adjacent section, the overlapping pairs of lugs being bent into locking engagement with one another.

ln addition, there has been provided a novel method forming the sectional floating roof by means of die punching the abutting peripheral walls of adjacent sections to form the overlapping pairs of lugs and then bending the overlapping lugs into engagement with each other.

Finally, there has been provided a novel floating roof of the character described, which comprises inner and outer roof sections all secured in place to one another by the means and method described above.

While there has been illustrated and described what is presently considered to be certain preferred embodiment of the invention, it will be understood that various modifications may be made therein which fall within the true spirit and scope of the invention.

What is claimed is:

1. A floating roof for use in a storage tank having an upstanding substantially cylindrical shell, said floating roof comprising a plurality of individually buoyant roof sections, each of said roof sections including a continuous peripheral wall therearound and a bottom wall closing the area defined by said peripheral wall, said roof sections being arranged substantially to fill the area defined by the associated shell with said peripheral wall of each roof section being disposed against the peripheral walls of the adjacent roof sections, each of said roof sections having a plurality of pairs of openings formed in and spaced around the peripheral wall thereof and a plurality of pairs of lugs spaced around said peripheral wall and extending therefrom, the lugs of each said pair of lugs being of equal length and being respectively integral with said peripheral wall adjacent to and between the openings of a corresponding one of said pairs of openings, certain of said pairs of lugs extending outwardly of said roof section and others in said pairs of lugs extending inwardly of said roof section, said roof sections being so arranged in the assembled positions thereof that said outwardly extending pairs of lugs are respectively received in corresponding ones of said pairs of openings in adjacent roof sections in overlapping relationship with corresponding pairs of inwardly extending lugs on said adjacent roof sections, said overlapping pairs of lugs being bent into locking engagement with each other for securing said roof sections one to another, and sealing means disposed between said roof sections and the associated shell to provide a vapor seal between said floating roof and the associated shell.

2. The floating roof set forth in claim 1, wherein each of said outwardly extending pairs of lugs is disposed in straddling relationship with a corresponding pair of inwardly extending lugs on an adjacent roof section.

3. The floating roof set forth in claim 1, wherein the distal ends of each of said outwardly extending pairs of lugs are respectively disposed in engagement with a corresponding pair of inwardly extending lugs on an adjacent roof section.

4. The floating roof set forth in claim 1, wherein each of said openings is disposed adjacent to the upper edge of the associated peripheral wall. 

1. A floating roof for use in a storage tank having an upstanding substantially cylindrical shell, said floating roof comprising a plurality of individually buoyant roof sections, each of said roof sections including a continuous peripheral wall therearound and a bottom wall closing the area defined by said peripheral wall, said roof sections being arranged substantially to fill the area defined by the associated shell with said peripheral wall of each roof section being disposed against the peripheral walls of the adjacent roof sections, each of said roof sections having a plurality of pairs of openings formed in and spaced around the peripheral wall thereof and a plurality of pairs of lugs spaced around said peripheral wall and extending therefrom, the lugs of each said pair of lugs being of equal length and being respectively integral with said peripheral wall adjacent to and between the openings of a corresponding one of said pairs of openings, certain of said pairs of lugs extending outwardly of said roof section and others in said pairs of lugs extending inwardly of said roof section, said roof sections being so arranged in the assembled positions thereof that said outwardly extending pairs of lugs are respectively received in corresponding ones of said pairs of openings in adjacent roof sections in overlapping relationship with corresponding pairs of inwardly extending lugs on said adjacent roof sections, said overlapping pairs of lugs being bent into locking engagement with each other for securing said roof sections one to another, and sealing means disposed between said roof sections and the associated shell to provide a vapor seal between said floating roof and the associated shell.
 2. The floating roof set forth in claim 1, wherein each of said outwardly extending pairs of lugs is disposed in straddling relationship with a corresponding pair of inwardly extending lugs on an adjacent roof section.
 3. The floating roof set forth in claim 1, wherein the distal ends of each of said outwardly extending pairs of lugs are respectively disposed in engagement with a corresponding pair of inwardly extending lugs on an adjacent roof section.
 4. The floating roof set fortH in claim 1, wherein each of said openings is disposed adjacent to the upper edge of the associated peripheral wall. 